The invention relates generally to laser velocimetry and more specifically concerns a direction sensitive laser velocimeter.
A serious limitation of prior laser velocimeters has been their inability to accurately indicate the direction of movement of particles in a sample volume under investigation. Several techniques for determining the direction of movement have been proposed and demonstrated. These techniques include color, polarization or frequency shifting to deduce direction. A disadvantage of the color technique is that it requires a two-color laser. A disadvantage of the polarization technique is that the polarizations are degraded by the optical elements and windows. A disadvantage of the frequency shifting techniques is that it has a narrow Doppler range.
The primary object of this invention is to provide a laser velocimeter that accurately indicates the direction of movement of particles in a sample under investigation.
Another object of this invention is to provide an optical technique for determining the direction of movement in laser velocimetry that lessens the disadvantages of prior art techniques.
Other objects and advantages of this invention will become apparent hereinafter and in the drawings.